Date: Mon, 08 Jun 2009 02:55:22 +0200 From: Ivan Voras <ivoras@freebsd.org> To: freebsd-fs@freebsd.org Subject: Re: ZFS v13 performance drops with low memory on FreeBSD-7 STABLE Message-ID: <h0hnil$r5h$1@ger.gmane.org> In-Reply-To: <4A2AA48B.20803@free.de> References: <4A2AA48B.20803@free.de>
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[-- Attachment #1 --] Kai Gallasch wrote: > Hi. > > I upgraded a server with 7-STABLE-amd64 and the MFC'd ZFS v13 about 8 > days ago. Since then the machine is running stable and this without > manually tuning vm.kmem_size, vfs.zfs.arc, etc. in loader.conf - so far > so good :-) > > In the last few days I noticed some performance issues with zfs, as some > customers complained about slow mysql database responses. > > MySQL is running in a database jail on a zfs v13 zpool, websites using > the mysql database are also running on zfs on the same server. > > The server is running about 30 in production jails, has 16GB RAM and 8GB > swap. Swap usage is about only 1% currently. > > After debugging the mysql settings for a while I found out, that when I > stopped some processes on the server that were using high amounts of > RAM, the datbase response times for queries were almost back to normal > again.. > > So for me this looks like when running applications and ZFS compete for > free RAM, ZFS looses. Is that so? Yes, that was the point of recent work in stabilizing ZFS - without it you would probably panic. With it, ZFS's memory is shrunk down. Unless there are other factors (like swapping; are you swapping on ZFS?), this is the probable reason for what you're seeing. It's kind of bad when the file system competes this directly with applications :( [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEARECAAYFAkosYXsACgkQldnAQVacBcg9OACdEi0W0QMOvjtHmZoay/BCcITg YPcAoKs4+xEUNx7gZdTH82yXGHAoUJ/0 =IQah -----END PGP SIGNATURE-----
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